refactor(desktop): unify New Agent selectors on the persona dropdown pattern

The Agent runtime, "Who can talk to this agent", and "Run on" fields
used raw <select> elements while the LLM provider/Model fields right
below them used PersonaDropdownField — the form read as two different
design languages. All selector-style controls in the create-agent form
now use PersonaDropdownField.

Also adds an isPlaceholder flag to PersonaDropdownOption so "Default"
provider/model options render faded like placeholder text instead of
looking like actively selected values.

Co-authored-by: Taylor Ho <taylorkmho@gmail.com>
Signed-off-by: Taylor Ho <taylorkmho@gmail.com>

desktop/src/features/agents/ui/AgentModelProviderFields.tsx

@@ -124,6 +124,9 @@ export function AgentModelProviderFields({
     : trimmedProvider || AUTO_PROVIDER_DROPDOWN_VALUE;
   const providerDropdownOptions: PersonaDropdownOption[] = [
     ...providerOptions.map((option) => ({
+      // The "Default" option means "no explicit provider" — render it faded
+      // in the trigger, like placeholder text.
+      isPlaceholder: option.id === "",
       label: option.label,
       value: option.id || AUTO_PROVIDER_DROPDOWN_VALUE,
     })),
@@ -131,6 +134,8 @@ export function AgentModelProviderFields({
   ];
   const modelDropdownOptions: PersonaDropdownOption[] = [
     ...modelOptions.map((option) => ({
+      // Same treatment for "Default model" — it's the absence of a choice.
+      isPlaceholder: option.id === "",
       label: option.label,
       value: option.id || AUTO_MODEL_DROPDOWN_VALUE,
     })),

desktop/src/features/agents/ui/CreateAgentDialog.tsx

@@ -40,6 +40,7 @@ import {
   ProviderConfigFields,
 } from "./ProviderConfigFields";
 import { CreateAgentRespondToField } from "./RespondToField";
+import { PersonaDropdownField } from "./PersonaDropdownField";
 import { RelayMeshAgentSection } from "@/features/mesh-compute/ui/RelayMeshAgentSection";
 import { meshPrepareRelayMeshClient } from "@/shared/api/tauriMesh";
 import type { MeshServeTarget } from "@/shared/api/tauriMesh";
@@ -501,8 +502,12 @@ export function CreateAgentDialog({
         <div className="flex max-h-[85vh] flex-col">
           <DialogHeader className="shrink-0 border-b border-border/60 px-6 py-5 pr-14">
             <DialogTitle>{draft?.title ?? "Create agent"}</DialogTitle>
-            <DialogDescription>
-              {draft?.description ??
+            {/* A draft with intentionally-blank description keeps the line
+                for screen readers only. */}
+            <DialogDescription
+              className={draft && !draft.description ? "sr-only" : undefined}
+            >
+              {draft?.description ||
                 "Set up a new agent and start it in this workspace."}
             </DialogDescription>
           </DialogHeader>
@@ -588,19 +593,19 @@ export function CreateAgentDialog({
                     >
                       Run on
                     </label>
-                    <select
-                      className="flex h-9 w-full rounded-md border border-input bg-background px-3 py-2 text-sm shadow-xs"
+                    <PersonaDropdownField
                       id="agent-run-on"
-                      onChange={(e) => handleRunOnChange(e.target.value)}
+                      onValueChange={handleRunOnChange}
+                      options={[
+                        { label: "This computer", value: "local" },
+                        ...backendProviders.map((p) => ({
+                          label: p.id,
+                          value: p.id,
+                        })),
+                      ]}
+                      placeholder="Choose where this agent runs"
                       value={runOn}
-                    >
-                      <option value="local">This computer</option>
-                      {backendProviders.map((p) => (
-                        <option key={p.id} value={p.id}>
-                          {p.id}
-                        </option>
-                      ))}
-                    </select>
+                    />
                   </div>
                 ) : null}
 

desktop/src/features/agents/ui/CreateAgentDialogSections.tsx

@@ -2,6 +2,7 @@ import type { AcpRuntime, ManagedAgentPrereqs } from "@/shared/api/types";
 import { cn } from "@/shared/lib/cn";
 import { Input } from "@/shared/ui/input";
 import { describeResolvedCommand } from "./agentUi";
+import { PersonaDropdownField } from "./PersonaDropdownField";
 
 export function CreateAgentBasicsFields({
   name,
@@ -55,19 +56,19 @@ export function CreateAgentRuntimeField({
       <label className="text-sm font-medium" htmlFor="agent-runtime">
         Agent runtime
       </label>
-      <select
-        className="flex h-9 w-full rounded-md border border-input bg-background px-3 py-2 text-sm shadow-xs"
+      <PersonaDropdownField
         id="agent-runtime"
-        onChange={(event) => onRuntimeChange(event.target.value)}
+        onValueChange={onRuntimeChange}
+        options={[
+          ...runtimes.map((runtime) => ({
+            label: runtime.label,
+            value: runtime.id,
+          })),
+          { label: "Custom command", value: "custom" },
+        ]}
+        placeholder="Choose a runtime"
         value={selectedRuntimeId}
-      >
-        {runtimes.map((runtime) => (
-          <option key={runtime.id} value={runtime.id}>
-            {runtime.label}
-          </option>
-        ))}
-        <option value="custom">Custom command</option>
-      </select>
+      />
       {selectedRuntime ? (
         <p className="text-xs text-muted-foreground">
           Detected via{" "}

desktop/src/features/agents/ui/PersonaDropdownField.tsx

@@ -34,6 +34,7 @@ export function PersonaDropdownField({
 }) {
   const [open, setOpen] = React.useState(false);
   const selectedOption = options.find((option) => option.value === value);
+  const showAsPlaceholder = !selectedOption || selectedOption.isPlaceholder;
 
   return (
     <div className={PERSONA_FIELD_SHELL_CLASS}>
@@ -52,7 +53,7 @@ export function PersonaDropdownField({
             <span
               className={cn(
                 "min-w-0 flex-1 truncate",
-                !selectedOption && "text-muted-foreground/55",
+                showAsPlaceholder && "text-muted-foreground/55",
               )}
             >
               {selectedOption?.label ?? placeholder}

desktop/src/features/agents/ui/RespondToField.tsx

@@ -12,6 +12,7 @@ import { cn } from "@/shared/lib/cn";
 import { Input } from "@/shared/ui/input";
 import { Textarea } from "@/shared/ui/textarea";
 import { UserAvatar } from "@/shared/ui/UserAvatar";
+import { PersonaDropdownField } from "./PersonaDropdownField";
 
 /**
  * Inbound author gate UI for create/edit agent dialogs.
@@ -30,6 +31,12 @@ import { UserAvatar } from "@/shared/ui/UserAvatar";
  * `desktop/src-tauri/src/managed_agents/types.rs`.
  */
 
+const RESPOND_TO_OPTIONS = [
+  { label: "Owner only (default)", value: "owner-only" },
+  { label: "Anyone", value: "anyone" },
+  { label: "Allowlist", value: "allowlist" },
+] as const;
+
 function formatSearchUserName(user: UserSearchResult) {
   return (
     user.displayName?.trim() ||
@@ -118,18 +125,14 @@ export function CreateAgentRespondToField({
       <label className="text-sm font-medium" htmlFor="agent-respond-to">
         Who can talk to this agent
       </label>
-      <select
-        className="flex h-9 w-full rounded-md border border-input bg-background px-3 py-2 text-sm shadow-xs"
-        data-testid="agent-respond-to-select"
+      <PersonaDropdownField
         disabled={disabled}
         id="agent-respond-to"
-        onChange={(e) => onModeChange(e.target.value as RespondToMode)}
+        onValueChange={(value) => onModeChange(value as RespondToMode)}
+        options={RESPOND_TO_OPTIONS}
+        placeholder="Choose who can talk to this agent"
         value={mode}
-      >
-        <option value="owner-only">Owner only (default)</option>
-        <option value="anyone">Anyone</option>
-        <option value="allowlist">Allowlist</option>
-      </select>
+      />
       <p className="text-xs text-muted-foreground">
         Controls which Nostr authors the agent listens to (@mentions, DMs,
         thread replies). The agent&apos;s owner can always shut it down with

desktop/src/features/agents/ui/personaDialogPickers.tsx

@@ -30,6 +30,12 @@ export type PersonaModelOption = {
 
 export type PersonaDropdownOption = {
   disabled?: boolean;
+  /**
+   * Marks an "auto"/default option that stands in for "no explicit choice".
+   * The trigger renders it faded, like placeholder text, so it reads as
+   * helper copy rather than an actively selected value.
+   */
+  isPlaceholder?: boolean;
   label: string;
   value: string;
 };

desktop/tests/e2e/persona-env-vars.spec.ts

@@ -320,7 +320,7 @@ test("agent model options follow the selected LLM provider", async ({
   const runtime = page.locator("#agent-runtime");
   const llmProvider = page.locator("#agent-llm-provider");
   const model = page.locator("#persona-model");
-  await expect(runtime).toHaveValue("buzz-agent");
+  await expect(runtime).toContainText("Buzz Agent");
   await expect(llmProvider).toBeVisible();
   await expect(model).toBeVisible();
   // Without live discovery, the only static option is "Default model".